In a large frying pan cook 1 tablespoon olive oil, 1 tablespoon butter and onions for 5 minutes. Add sugar and sprinkle a little salt and pepper on it. Turn heat to low and cook for about 40 minutes, stirring every 10 minutes. The onions should be golden brown and caramelized.

Heat broth in a large pan. Add miso and stir until completely dissolved. Add caramelized onions and soy sauce. Season to taste. You can make this ahead and reheat to serve.

Preheat oven to 350F.

Lay 6 pieces on parchment paper on a flat surface. Divide mushrooms equally in parchment squares. Add garlic and drizzle truffle oil on top. Sprinkle salt and pepper and close pouches with twine.